The present invention relates to coating formulations for paper, film and other substrates which are receptive to common, aqueous ink jet inks and form images exhibiting superior quality when compared to uncoated paper, film and other printable substrates. More specifically, the present invention relates to cationically modified coatings which render the printed images waterfast. The present invention also relates to methods of coating various printable substrates utilizing said coatings as well as materials coated with said coatings.
The ink jet method of printing is a rapidly growing, commercially important printing process because of its ability to produce economical, high quality, multi-colored prints. In fact, ink jet print methodology is becoming the print method of choice for producing colored hard copy of computer generated images consisting of graphics and fonts in both narrow and wide format. Ink jet printing is a non-impact and non-contact printing method in which an electronic signal controls and directs droplets or a stream of ink that can be deposited on a wide variety of substrates. Current ink jet printing technology involves forcing the ink drops through small nozzles by piezoelectric pressure, thermal ejection, or oscillation, and onto the surface of a material/media. Ink jet printing is extremely versatile in terms of the variety of substrate material that can be treated, as well as the print quality and the speed of operation that can be achieved. In addition, ink jet printing is digitally controllable.
For these reasons, ink jet printing methodology has been widely adopted for industrial marking and labeling. In addition, ink jet printing methodology has also found widespread use in architectural and engineering design applications, medical imaging, office printing (of both text and graphics), geographical imaging systems (e.g., for seismic data analysis and mapping), signage, in display graphics (e.g., photographic reproduction, business and courtroom graphics, graphic arts), and the like. Finally, ink jet printing has now also been used to create an image on a variety of textile substrates.
Both dyes and pigments have been used as colorants for such ink jet ink formulations. However, such materials do not always adhere well to the substrates to which the ink is applied. For example, dyes may dissolve upon a printed substrate""s contact with water. Thus, images applied employing ink jet printing methodology may tend to run or smear upon repeated contact, or may be actually removed from the printed surface if exposed to substantial quantities of aqueous media (e.g., if an ink jet printed article is exposed to water or comes in contact with water through other means). There is therefore a need in the art for coatings which enhance the waterfastness capabilities of various substrates, in particular when aqueous based inks are to be employed on said substrates. It is to such need that the present invention is directed as the coatings of the present invention have proven particularly effective in improving waterfastness.
In accordance with the present invention, media coatings for use on substrates for ink jet printing include a cationically modified clay, a cationically modified silica and a binder. Alternatively, the media coatings also include additional additives. In particular, in one embodiment of the invention, the media coatings also include a surfactant. The ratio of cationically modified clay to cationically modified silica varies in the coating formulation from about 1% to about 99%. Desirably, the ratio of the cationically modified clay to cationically modified silica varies from about 10% to about 50%. More desirably, the ratio of cationically modified clay to cationically modified silica varies from about 25% to about 35%. The ratio of the total cationically modified clay and cationically modified silica to binder varies from about 20% to about 80%. Desirably, the ratio of the total cationically modified clay and cationically modified silica to binder varies from about 65% to about 75%.
These and other features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended claims.